1. Field of the Invention
The present invention relates to an ejector apparatus for a fuel cell which the apparatus is incorporated in a fuel cell system and mixes a fuel offgas, which is exhausted from the fuel cell, with a fuel gas newly supplied and recirculates the fuel offgas.
2. Description of the Related Art
For example, in a fuel cell system, in order to enhance a power-generation efficiency of a fuel cell, it is used an ejector that mixes a fuel offgas (hydrogen offgas), which is exhausted from the fuel cell, with a fuel gas (hydrogen gas) newly supplied and recirculates the fuel offgas.
Regarding this kind of ejector, for example, according to Japanese Patent Laid-Open Publication No. 2009-144557, it is disclosed an ejector that comprises a first fluid chamber where a hydrogen gas is supplied, a bar-like needle, a nozzle for discharging the hydrogen gas supplied to the first fluid chamber from a discharge port (nozzle hole), a second fluid chamber where a hydrogen offgas is introduced, a diffuser provided on a discharge-port side of the nozzle, and a third fluid chamber where air is supplied. The ejector is configured so that: the first fluid chamber is provided between the second fluid chamber and the third fluid chamber; the first fluid chamber and the second fluid chamber are partitioned by a first diaphragm; the first fluid chamber and the third fluid chamber are partitioned by a second diaphragm having a same pressure receiving area as the first diaphragm; and the needle and the nozzle are separated from each other by pressure of the air introduced into the third fluid chamber and are made to approach with each other by pressure of the hydrogen offgas introduced into the second fluid chamber.
According to the ejector disclosed in the Japanese Patent Laid-Open Publication No. 2009-144557, due to the air supplied to the third fluid chamber and the hydrogen offgas introduced into the second fluid chamber, since directions in relatively moving the needle and the nozzle are made opposite and cancel each other, it is assumed that even if supply pressure of the hydrogen gas supplied to the first fluid chamber fluctuates, a flow rate of a hydrogen gas (mixed gas) discharged from the discharge port of the nozzle can be constant.
Incidentally, according to the ejector disclosed in the Japanese Patent Laid-Open Publication No. 2009-144557, there is a problem that when the supply pressure of the hydrogen gas supplied to the first fluid chamber is applied, the nozzle results in being displaced toward an opening side. It is inferred that this is due to, for example, an area of a seat portion, which is a base face, of the nozzle; hydrogen-gas discharge pressure from the nozzle hole; and the like.